1. Field
The present disclosure relates to an automatic transmission.
2. Description of the Related Art
An automatic transmission capable of providing 8-forward-speed transmission using a first planetary gear set for input, second and third planetary gear sets for varying the speed, and six engagement mechanisms has been developed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2005-273768).
According to Japanese Unexamined Patent Application Publication No. 2005-273768, the first planetary gear set for input is formed as a double pinion planetary gear set. In addition, each of a second planetary gear set and a third gear set for varying the speed is formed as a Ravigneaux planetary gear set. The six engagement mechanisms include four wet multiple disc clutches and two brakes.
For example, as indicated by a detailed diagram in FIG. 2 of Japanese Patent No. 4711869, the automatic transmission includes eight trains along the axis line of the input shaft. More specifically, beginning with the side closest to the torque converter, a first train is formed from a fourth wet multiple disc clutch, a second train is formed from a first planetary gear set, a third train is formed from the first wet multiple disc clutch, a fourth train is formed from a third wet multiple disc clutch (note that although the third wet multiple disc clutch seems to be in the same train as the first planetary gear set in a skeleton diagram, a piston and a hydraulic pathway for a third clutch are formed between the first wet multiple disc clutch and an output gear, in reality), a fifth train is formed from the output gear, a sixth train is formed from a second planetary gear set, a seventh train is formed from a third planetary gear set, and an eighth train is formed from a second wet multiple disc clutch.